November 26, 2012

Medieval signal of Swedish (?) admixture in Finland

I took the FIN (Finnish), GBR (British), and CDX (Chinese Dai) samples of the 1000 Genomes Project, each of which has a sample size of 100 in order to investigate the signal of East-West Eurasian admixture in Finns. While neither Britons nor Dai could be imagine of having contributed to Finns directly, they ought to make useful proxies of a NW European population lacking recent East Eurasian ancestry, and an East Eurasian population lacking recent West Eurasian ancestry respectively.

In the following, I will assume a generation length of 29 years and a sample birthyear of 1980 as in previous experiments.

First, the 1-reference analysis of FIN using GBR produced an admixture proportion lower bound of 37.4 +/- 5.1 percent.

The corresponding analysis of FIN using CDX produced an admixture proportion lower bound of 4.4 +/- 1.0 percent.

The 2-ref admixture test with {GBR,CDX} reported success:

Test SUCCEEDS (z=2.76, p=0.0057) for FIN with {GBR, CDX} weights

But, the decay rates were inconsistent, a situation which might occur when major admixture from different sources took place at different times. In particular, the one using CDX corresponded to 65.57 +/- 8.36 generations, and the one using GBR to 25.48 +/- 4.93 generations.

In calendar dates, Finns are estimated to have mixed with an East Eurasian CDX-like population between 170BC-320AD and with a NW European GBR-like population between 1100-1380AD.

The central date of the latter estimate is 1,240AD, which corresponds quite closely to the beginning of Swedish rule and is in the middle of the 13th. century, between the time when Finland was initially claimed for western Christendom (12th c.) and the time when the conflict between Sweden and Russia was settled (14th c.).

6 comments:

Limited permanent settlement from "Sweden" - a work in progress still then when it comes to the political entity - on coastal areas in Finland seems to have preceded political control and started sometime after 1000 based on archaeological evidence. After southern Finland became politically tied to Sweden there seems to have been more emigration from Sweden, but in such numbers that except on some coastal areas the settlers were assimilated. But the settlers didn't come only from Sweden; in the small coastal trading towns there were German settlers and there's evidence of limited numbers of Germans settling as farmers inland during the late Middle Age. The ties this far might be earlier than Swedish political control and connected to Baltic maritime trade in the early Middle Age; the spread of burial of bodies instead of cremation spread through southern Finland between 700-1000 and might be influenced by example of long distance traders as it preceded the spread of Christianity, which started after 1000 but before the supposed Swedish crusades. On the other hand, Åland Isles were colonized from the Swedish mainland starting already from 400 CE, replacing the earlier small population there, and like in later times, the sea between Finland and Sweden probably united the coastal areas more than it separated them. Another thing is movement from Finland to Sweden; there was a large-scale emigration of Savonians to northern and central Sweden starting from the late 16th century. This population, called the "Forest Finns" in Sweden, is now basically totally assimilated, but their contribution to current Swedish gene pool is relatively extensive and would cloud the picture when one would go farther and compare Finns and Swedes directly.

I was studying this a while ago in regards to Multiple Sclerosis and Lactose Tolerance. The west and south parts of Finland were occupied by Swedes and Danes. They are lactose tolerant and they also have a high rate of MS. Eastern Finland population are northern Eurasian. They have a low rate of MS and are lactose intolerant. In fact there are families where even babies are lactose intolerant at birth.

I was wondering some time ago if the huge, very interesting chromosome 2 may contain the clue to MS. As in somewhere near the gene for 'lactase' there is also the gene which predisposes to MS.

It can't be a coincidence that the worldwide distribution of MS is also correlated with the distribution of ability to digest lactose into adulthood.

The time of the Eastern admixture seems to correspond to East Germanic (Gothic)migrations to the east which might have caused wide geographical perturbations among the local Baltic and perhaps Slavic tribes making them move to other areas.

Connections between British Isles and Finland were not impossible. This is historically known, but the strongest evidences can be found in yDna and mtDna proportions. While the Swedish yDna is very rare in Finland, we have a lot of Western European (including British Isles, Ireland and Scotland) mitochondrial dna, for example HVR1 and HVR1+HVR2 matches. This conflicts strongly with the idea that the western admix in Finland would be almost totally from Sweden. We dont yet even speak about the Baltic direction...

@rouge77

So called Forest Finnish group was not biggest known migration to Sweden. During the 18th century wars only Stockholm received 12000 Finnish war refugees, mainly from the coastal areas in Finland. Middle Sweden received around the same amount of refugees. Many coastal towns in Finland emptied totally to Sweden, because civilians were very afraid of the Russian brutality. Some came back after the war, but not all. These towns in Finland got partly new residenst from east. Because the gene flow to Sweden has been strong to recent days I dont fully agree ideas about separating "true Swedes" and Finnish admix. Without research we ven dont know how the Finnish admix looks in Swede. It is not possible by any demographic way to make this separation, only by cutting arbitrarily results after genetic analyses to pure Swedes and mixed Swedes.

Davidski, I'm a dentist I'm not an anthropologist. How would you define the Asiatic influx? Clearly I was inaccurate. I do know that the people migrated from the east are different from the coastal Finns who came from Scandinavia.

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